The present invention relates to a method for fabricating a semiconductor device, and more particularly to a method for planarizing insulating films.
A multi-level interconnection structure is required in a highly integrated circuit. Planarization of an inter-layer insulating film used in the structure comes to be important. In the past, it is known that a spin-on-glass is used to planarize the inter-layer insulating film. For example, first, low-level wirings are formed on a surface of a substrate. Then, a first insulating film is formed on the surface of the wirings and the substrate. Existence of the wirings is reflected in uneven surface of the first insulating film. Then, a spin-on-glass film is formed on the first insulating film to planarize the uneven surface of the first insulating film. Then, a second insulating film is formed on the spin-on-glass film. Then, upper-level wirings are formed on the second insulating film. Through these processes, a two-level interconnection structure having improved plane surface of inter-layer insulating film is complicated. However, evenness cannot coexist with reliability of the insulating films.